Thiophene derivatives, particularly those which are substituted in the 3-position and/or 4-position by way of an oxygen atom, are suitable initial materials for preparing electrically conductive polythiophenes. For the purpose of achieving high electrical conductivities in this connection, the purity of the thiophene derivatives plays a crucial role. Ordinarily, distillation is used as a conventional purification process for thiophene derivatives.
But it has now become evident that the thiophenes that have been purified in this way have a tendency in the course of storage towards changes in color and/or the formation of undesirable secondary components, such as, for example, the formation of dimers. This results in considerable impairment of the properties of the polythiophenes prepared therefrom.
Consequently there has continued to be a demand for a process for stabilizing such thiophene derivatives, in order to avoid the changes in color or formation of secondary components described in the foregoing, and hence to make thiophene derivatives available that also after storage exhibit sufficient purity for further processing into electrically conductive polythiophenes.
Consequently, one object of the present invention includes providing such a process, and hence, thiophene derivatives of suitable quality.